JEC COMPOSITES MAGAZINE - Issue #67 - August/September 2011 - 27

voids and reduced volatiles. Phenolic prepregs for ballistic components involve the use of fibres such as Kevlar and S-glass with resole resin. In addition to the large quantities of ballistic products needed in armed conflicts in Iraq and Afghanistan, other areas require ballistic materials for vehicles in foreign nations with political unrest, buildings for blast containment, etc. Some preliminary efforts have utilized pultrusion to fabricate composite armour involving a multi-material approach for optimized performance that consists in using layers to blunt or capture projectiles as well as to prevent fire. The insertion of ceramics appears possible using this method.

materials (bisphenols or novolak), primary amines, and formaldehyde. The ringopening polymerization of BZ does not generate by-products nor volatiles and enhances the excellent dimensional stability of the final product. Besides high heat resistance and flameretardant properties, BZ resins ChinaGrate Composite exhibit characteristics that are Structures (Nantong) reported not observed in traditional the use of high amounts of phenolic resins such as low aluminium hydroxide with water absorption and stable, low resole resin (0.05-0.3:1) with dielectric properties for alkali-free glass fibre yarn and electronic materials, fibretemperatures of 220-250°C to reinforced composites, and obtain a product which adhesives. Huntsman, possesses an unusually high Momentive, Henkel and temperature ablation Sumitomo Bakelite are the main resistance of 927°C and meets producers of BZ resins. US Coast Guard Level 2 conditions [2]. Calidur™ is a new generation of single-component, roomtemperature-stable polyaryl ether amide thermoset matrix resins that was introduced by Evonik Degussa [3] to the aerospace and electronics industries within the past year. Robust mechanical properties are obtained using this technology, involving curing at 140°C for 2 hours with a Tg of 195°C. These polyaryl ether amides show promise as a new choice for advanced composite design due to exceptional Fig. 2: The Trabant body is a phenolic/cotton fibre composite still resin/fibre adhesion, the basis operating in Germany after more than 50 years! for high compressive and shear Filament winding New systems strength. The potential to Filament winding with Benzoxazines (BZ) have been introduce improved technology phenolic resins has provided developed as a novel type of for interior aircraft applications the semi-conductor industry phenolic resins. They differ requiring stringent FST with flame- and corrosionfrom traditional phenolics in performance, as well as exterior resistant ducts for clean rooms, that the phenolic moieties are structural applications requiring with Factory Mutual connected through the hot/wet integrity, is intriguing. certification. Filament-wound formation of a cyclic structure The new formulation allows its products can be used as rather than the methylene [use in a variety of cost-effective electrical conduits in the CH2-] bridge associated with alternatives to medium- and hydro-electric and traditional phenolics. high-Tg epoxies, BMI, and underground transportation Benzoxazines are easily cyanate ester resins for highindustries. prepared from phenol-type performance, demanding Pultruded phenolic components for offshore oil platforms continue to be in great demand as more crude oil is being discovered offshore. Resoles are the preferred type of phenolic resin for this process.

Pultrusion

application sectors such as aerospace, transportation, automotive, electrical/ electronics and others (see Figures 1 and 2).

Trends
More favourable conditions for the fast curing of resoles at 120°C or lower are in great demand for most industrial applications requiring good surface appearance. The FST characteristics carry over to appended resin systems such as cyanate esters, ring-formed (BZ) or ring-opened (Calidur™) systems with the additional advantage of reduced byproduct emissions or low volatile generation. However, cyanate esters and BZ are brittle and require modest toughness. Some improvement in toughness can be achieved in these resin systems but require multicomponent systems and questionable uniformity in the final cured composite. Presently, Calidur™ appears to provide the many favourable features that manifest themselves in attractive highperformance composites: no volatiles emitted, low cure exotherm, low cure shrinkage, high thermal strength, good hot/wet strength, high compression and shear strength in composites, and excellent toughness.
More information: lapilato@optonline.net References

No67 August - September 2011 / jec composites magazine

1 . L. Pilato (Ed.), Phenolic

Resins: A Century of Progress. Springer, Heidelberg, 2010 2 . Z. Shatong and X. Hanxian, CN 101649105, February 17, 2010 3 . Evonik Degussa Calidur™ literature

Market

JEC COMPOSITES MAGAZINE - Issue #67 - August/September 2011

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #67 - August/September 2011